Why are mitochrondrial genomes so fast evolving? - (Aug/20/2006 )

Does anyone know why it is that mitochondrial genes should be less conserved than nuclear genes?

It doesn't make sense to me.

They are only maternally inherited and so don't recombine, and most of the genome is protein coding and is transcribed, rather than introns and 'junk'.

Yet it seems to be the case and so there must be a good explanation?

I am not sure that a mitochondria has a proofreading system that is as good as the one in the nuclei, most likely it does not. Also high concentration of oxidants exist in mit (generated as by-products during energy production process) could be a contributing factor for a higher rate of DNA damages and mutations that exceeds that for chromosomal DNA in the nuclei.